Electronic equipment, such as mobile communication devices, is subject to various electronic tests after production. Such tests are generally necessary to ensure proper configuration, calibration and functionality of various elements of the devices under test (DUT). DUTs may be both passive and active devices. For testing purposes, specific testing devices are employed which simulate a testing environment under predefined testing conditions. For example, testing devices may employ one or more specific testing routines with predefined testing schedules. Those testing schedules regularly involve input of particular test signal sequences into the DUT and/or reception of responses to testing signals input to the DUT. Such responses may be evaluated for consistency, constancy, timeliness and other properties of an expected behavior of the DUT.
Quite often it is not possible to completely characterize all DUTs using just a single piece of test equipment. Instead, a variety of stimuli and responses are required to sufficiently measure linear and non-linear behavior of the DUT. Network analyzers (NA), such as scalar network analyzers (SNA) or vector network analyzers (VNA) are designed measure both linear and non-linear behavior of DUTs with various measurement schemes such as for example swept frequency schemes, swept power schemes, combined swept frequency and power schemes or the like.
Components or circuits passing electromagnetic signals are subject to various undesired or unavoidable influences like signal distortion, signal reflectance or frequency-dependent amplitude and phase shifts (linear influences) or intermodulation distortion (non-linear influences). One of the important testing concepts sets out to determine the reflectivity and transmission of electronic equipment with respect to high-frequency electromagnetic signals that are input to an interface port of the electronic equipment. To that end, 2-port transmission measurements are conducted to verify simulation models and measure performances of hardware prototypes in order to ensure expected behavior and accurate specifications of the equipment.
For frequency-dependent measurement and testing schemes, a combination of network analyzers with front-ended frequency converters is used to extend the frequency range of testing and test response signals into the sub-millimeter and millimeter wavelength regime. Frequency converters employ frequency multipliers to transform a RF source signal supplied at one of the ports of the network analyzer into a stimulus signal of increased frequency. Test signals and reference signals are separated using a directional coupler and both signals are down-converted into the basic frequency regime of the network analyzer using harmonic or sub-harmonic mixers.
Due to the inherent electronic characteristics of the components used in the circuitry of the frequency converters, the converters themselves are subject to non-linear output characteristics, for example a non-linear frequency dependence of the ratio of output power to input power. Typical measurement schemes, however, require linear frequency and/or power sweeps for the testing signals input to DUTs. Thus, it may be possible to determine characteristic curves of the converters and to normalize the output of the converters based on the determined curves.
Document U.S. Pat. No. 6,888,342 B2 discloses a combined handheld spectrum analyzer and vector network analyzer where an EPROM provided on a control PCB stores calibration curves of frequency dividers and amplifiers in the vector network analyzer. Document DE 10 2012 218 948 A1 discloses a computer system for pre-distorting input signals to a microwave generator on the basis of a system model.
It would, however, be desirable to find solutions for configuring frequency converters in testing environments that offer more flexibility and do not require separating configuration measurements to be undertaken at the testing site.